274 MORPHOLOGY AND EVOLUTION
absolutely, and relatively to the size of the body, smaller than the human brain. It is also much smaller than the endocranial casts of the skulls of fossil men. These facts are shown in the following table, wThich is partly based on figures in the " Guide to the Fossil Remains of Man " in the British iluseum.
Brain of Gorilla ......
„ „ Australian native Endocranial cast of the Rhodesian Man „ „ „ Piltdown-Skull
Brain of European......
Endocranial cast of the Neanderthal !
5So c.c. 1,250 c.c. 1,230 c.c. 1.800 c.c. 1,480 c.c. 1,626 c.c.
Relation to body weight
1 150—1 '200
Keith (97^ calculated the weights and ratios in Apes, and he has shown that the cranial capacity in cubic centimetres is not an index of the weight in grammes, Still the cranial capacity is a useful comparative standard. Keith's observations have shown that the human brain grows relatively more than that of the Apes, for the brain of the human infant is 36 per cent, of the adult brain, and the simian infantile brain is 70 per cent, of that of the adult.
Every llammal is brought into relation with its environment through the organs of special sense and the nerve-endings in the skin. The impressions made on these structures induce stimuli which pass centri-petally to different parts of the cerebrum. The olfactory stimuli pass via the piriform area and fascia dentata to the hippocampus, where they possibly meet gustatory stimuli. The visual and auditory stimuli, as well as those of general sensibility (temperature, touch and